My latest scope needs a new eq platform because of the high CG. I'm almost done with this one except for some sanding, varnishing and bolting down the motors but so far it's cost only $29.5. That doesn't count the maple plywood I already had, ball bearings I had and some screws and leveling feet I need to get yet. It'll be done before the scope!2 motors from Apogee @ $4 each2 3 inch Newport SS rods @ $6.60 eachmaple from Home Depot $8.30

Here is the bottom board. The 1/15 rpm motors from Apogee are CCW so they must go behind the north bearing. I drilled our the smaller tapped hole on th post to 4 mm to match the motor shafts on a lathe. The SS posts from Newport are 1/2 inch so the radius of the north bearing is 23.93. The CG above the middle of the board is 17.6 inches. Total height 4.25 in. If you want I can start another thread on how I made it.

As you see it isn't finished yet but it's almost exactly like my first platform (which tracks great)except that I'm not going to knurl the Newport posts. I don't think it'll be necessary. I can always knurl it later if need be.

My latitude is 39.25 degrees and my rocker box is 18 inches square so I started with a platform 19 inches wide and long.. Shown below is the cross section layout. The south bearing is 11.91 inches radius spaced 18 inches from the north bearing. The mid platform CG is 17.6 inches from the platform but my computation for the scope CG is 14 inches, 3.6 inches lower but I donâ€™t think itâ€™s a problem at all.

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I cut two boards with a 50.75 degree bevel about 4.5 inches X 20 inches. On the back side I tacked a Â¼ inch scrap piece of plywood and measured from about where the tape is to a 23.93 inch arc from each side. I drilled a hole for a finishing nail to pivot on at that point

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On my table saw I bolted a Â¾ inch piece of wood with my finishing nail pivot a little more than 24 inches from the blade. The blade was tipped at 50.75 degrees and lowered all the way down. I raised the blade a 1/16 of an inch at a time and swung the board into the blade slowly pivoting on the nail. I raised it another 1/16 th and repeated. Eventually the blade was above the board and it was roughed out. I then switched to a sanding disk and continued, moving the part a small distance into the disk each time until the radius was 23.93 at the midpoint. This makes beautiful smooth bearings (and I have fun doing this as well).

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I glued a 1.5 X 4.5 inch piece of maple to the inside of two 24 X 2.5 inch pieces. This is for mounting the motor. I drilled a Â½ inch hole in two pieces of teflon and cut them into for bearings. 2 cross-pieces of maple were glued for strength. (I taped the posts and bearings in place temporarily to figure out where the cross pieces should go.)

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3 pieces of maple were cut to hold the bearings. The rear bearing block was easy, the other two were compound angles and it took a number of tries cutting pieces on a band saw to get the angles right so that the ball bearings races ran flat to the bearings. These little pieces were the trickiest part of the project.

The motors i used are 1/15 RPM AC timing motors CCW rotation 110 volt 60 hz 1.35 watts by Sonceboz. I just checked Apogee's website and sorry they no longer have them it seems. However Herbach and Rademan has this motor for $18.95. here
It is clockwise however which means the motor must be mounted in front of the north bearing.